reference passing

[Noel Wood]

Hello, I have a function I use to remove all the whitespace from the
beginning and end of all the $_REQUEST variables. A $_REQUEST variable may
also be an array so I call it recursively. I have used as a formal
parameter a referenced passed variable. So any changes to the array inside
the function should also occur to the array outside the function.
The function I use is shown below...

//the array pointer must be reset to the start before this function is
called
// for the first time. It would be a safe idea to call
resset($inputVa riable) after last use as well.
function removeWhitespac eRecursively(&$ anArray){
while (list($key,$val ) = each ($anArray)){
if (is_array($val) ){
removeWhitespac eRecursively($v al);
$anArray[$key] = $val; //unknown why required.
}else{
$anArray[$key] = trim($val);

}
}
}
In testing this function. It worked well for simple $_REQUEST variables
that had no arrays in them but when an array was in the $_REQUEST array then
the line marked "//unknown why required" was found to be needed otherwise
the changes to the recursively altered array did not propagate to the
original array.
eg...
given the input...
$_REQUEST['name'] = " noel ";
$_REQUEST['phone'][0] = " 1234 ";
$_REQUEST['phone'][1] = " 5678 ";

The output without the marked line was...
$_REQUEST['name'] = "noel";
$_REQUEST['phone'][0] = " 1234 ";
$_REQUEST['phone'][1] = " 5678 ";

The output with the marked line was...
$_REQUEST['name'] = "noel";
$_REQUEST['phone'][0] = "1234";
$_REQUEST['phone'][1] = "5678";

Can anyone please explain why the changes to the recursively changed array
did not propagate to the original array?
Thanks for your help.

[Mike Duganets]

Re: reference passing



Noel Wood wrote:
[color=blue]
> Hello, I have a function I use to remove all the whitespace from the
> beginning and end of all the $_REQUEST variables. A $_REQUEST variable may
> also be an array so I call it recursively. I have used as a formal
> parameter a referenced passed variable. So any changes to the array inside
> the function should also occur to the array outside the function.
> The function I use is shown below...
>
> //the array pointer must be reset to the start before this function is
> called
> // for the first time. It would be a safe idea to call
> resset($inputVa riable) after last use as well.
> function removeWhitespac eRecursively(&$ anArray){
> while (list($key,$val ) = each ($anArray)){
> if (is_array($val) ){
> removeWhitespac eRecursively($v al);
> $anArray[$key] = $val; //unknown why required.[/color]

$val - is a copy of array $anArray[$key]
you pass copy to your function, modify it
and after thar you _must_ assign it to your
target output array $anArray[$key]
[color=blue]
> }else{
> $anArray[$key] = trim($val);
>
> }
> }
> }
> In testing this function. It worked well for simple $_REQUEST variables
> that had no arrays in them but when an array was in the $_REQUEST array then
> the line marked "//unknown why required" was found to be needed otherwise
> the changes to the recursively altered array did not propagate to the
> original array.
> eg...
> given the input...
> $_REQUEST['name'] = " noel ";
> $_REQUEST['phone'][0] = " 1234 ";
> $_REQUEST['phone'][1] = " 5678 ";
>
> The output without the marked line was...
> $_REQUEST['name'] = "noel";
> $_REQUEST['phone'][0] = " 1234 ";
> $_REQUEST['phone'][1] = " 5678 ";
>
> The output with the marked line was...
> $_REQUEST['name'] = "noel";
> $_REQUEST['phone'][0] = "1234";
> $_REQUEST['phone'][1] = "5678";
>
> Can anyone please explain why the changes to the recursively changed array
> did not propagate to the original array?
> Thanks for your help.
>
>[/color]

[Jasper Bryant-Greene]

Re: reference passing

Noel Wood wrote:
[color=blue]
> function removeWhitespac eRecursively(&$ anArray){
> while (list($key,$val ) = each ($anArray)){
> if (is_array($val) ){
> removeWhitespac eRecursively($v al);
> $anArray[$key] = $val; //unknown why required.
> }else{
> $anArray[$key] = trim($val);
>
> }
> }
> }
>
> Can anyone please explain why the changes to the recursively changed array
> did not propagate to the original array?
> Thanks for your help.[/color]

Because when you get list($key,$val) out of $anArray you are making a
copy of the variable, not a reference to the variable. You can work
around this by passing $anArray[$key] to removeWhitespac eRecursively()
when calling it from within the function.

A better way to implement this function would be:

function removeWhitespac eRecursively(&$ anArray) {
foreach($anArra y as $key=>$val) {
if(is_array($va l))
removeWhitespac eRecursively($a nArray[$key]);
else
$anArray[$key] = trim($val);
}
}

--
Jasper Bryant-Greene
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